Hitherto, there have been proposed many methods for improving the impact resistance of thermoplastic resins such as polyamide resin and the like. For example, a method of blending a thermoplastic resin and a polyorganosiloxane graft copolymer, which is described in Japanese Patent Application Kokai No. 61-235462 and No. 2-1763, is a relatively good method. In this method, however, dispersion of the polyorganosiloxane graft copolymer depends upon interaction between the polymer constituting the outermost layer of the graft copolymer and the matrix resin, so that there is a case wherein an improvement in impact strength is insufficient depending upon properties of the matrix resin. Consequently, resin compositions developing a higher impact resistance are being demanded.
In view of the situation as mentioned above, the present inventors have extensively, studied to improve the impact resistance of polyamide resins, polymethacrylimide resins and polyetherimide resins over a wider temperature range. As a result, the present inventors have found that thermoplastic resin compositions having improved impact resistance over a wider temperature range and also being superior in heat resistance, appearance of molded product and adhesion property cf paint film are obtained by blending these thermoplastic resins with a polyorganosiloxane graft copolymer obtained by graft-polymerizing one or more kinds of vinyl monomer onto a polyorganosiloxane rubber or a polyorganosiloxane compound rubber having such a structure that the polyorganosiloxane rubber component and polyalkyl (meth)acrylate rubber component cannot be separated from each other, and an organic silane compound having an epoxy group. The present inventors thus attained to the present invention.